What characteristic do firestop putties have before heat exposure?

Firestop putties are specifically designed to maintain their effectiveness during scenarios such as a fire. Before exposure to heat, the characteristic that defines firestop putties is their ability to remain soft and pliable. This pliability allows the putty to effectively seal gaps and openings, providing a barrier against the passage of smoke and flames. In a fire situation, the putty is intended to activate, hardening and expanding to fill voids and maintain structural integrity.

This softness before exposure also facilitates easy application, allowing technicians to mould and shape the putty as needed to fit various installation scenarios. This characteristic is critical because it ensures that the firestop material can be adequately compliant with the surfaces and conditions it encounters, providing an optimal seal against fire and smoke spread.